A relatively new technique for constructing a ceramic to metal crown from a foil coping is disclosed in U.S. Pat. Nos. 4,459,112 and 4,492,579, respectively. The foil coping is formed from a thin metal foil starting material, preferably in the form of a laminate of precious metal layers with a composite thickness of between 15-100 mils. The foil is prefolded into a geometrical form having a plurality of foldable sections which extend radially from a central, preferably unfolded central area. In the preferred embodiment, the foldable sections form pleats which overlap each other when folded over. The recommended procedure for forming the coping from the foil is to place the geometric form over the die of the tooth to be restored and to fold over each section in sequence, either clockwise or counterclockwise. Each folded section may also be burnished to remove any trapped air spaces and to tightly engage the folds to the die in an overlapping relationship. After burnishing the foil is ready to be swaged. The swaging operation more accurately adapts the foil to the die to form a coping which replicates the shape of the die.
Dental swaging devices are not new. Fundamentally, the swaging instrument consists of a female die and a male punch. The die of the tooth to be restored is mounted in the female die. A metal form such as a foil coping is mounted over the die in alignment with the male punch. The male punch is then struck repeatedly with a hammer or mallet until the form is compressed into adaptation against the die.
Since the die of the tooth is composed of ceramic or other fragile composition and since the metal coping is also relatively thin, it has heretofore been necessary to incorporate highly viscous plastic compound such as clay in a putty-like consistency into the swaging device between the male punch and the die to protect the foil coping from tearing and to prevent damage to the die. After each use of the swager, the foil coping must be removed from the putty-like compound, which is not only a very time-consuming operation but is also impractical. Moreover, although the putty-like compound protects the foil coping and the die of the tooth, it requires the operator to consistently hit the male punch many times over and with substantial force. Accordingly, it is difficult to assure reproducible quality.
It is therefore the principal object of the present invention to provide a dental swager which overcomes all of the disadvantages of conventional dental swagers.